Which command is known for running a subsearch that iterates over multiple fields?

The command that is known for running a subsearch that iterates over multiple fields is the foreach command. This command allows users to specify a list of fields and then apply a specified operation or expression to each field in turn. By using foreach, analysts can streamline data processing within their searches, making it particularly useful for iterating through a set of values or fields, such as applying a transformation or filter.

For instance, when you have multiple fields and want to perform calculations or searches across them, foreach can execute the desired operation for each field separately, effectively automating repetitive tasks. This is particularly advantageous in scenarios where data from multiple sources or attributes needs to be analyzed concurrently.

In contrast, while the subsearch command is used to perform a search inside another search, it does not inherently iterate over multiple fields in the way foreach does. The map command also executes subsearches but is designed for applying a specified search command to each result of the outer search, rather than for iterating over multiple fields. The eval command, on the other hand, is primarily used for creating or modifying fields based on expressions and does not facilitate subsearch execution across multiple fields. Thus, foreach stands out as the correct command for this function.